LONDON, April 14 (Reuters) - British Prime Minister David Cameron and German Chancellor Angela Merkel on Monday called on Russia to unequivocally condemn the occupation of government buildings in eastern Ukraine.

The two leaders spoke by phone on Monday to discuss escalating tensions and the threat of Ukrainian military action following the occupation of state buildings in the east of Ukraine by pro-Russian separatists.

"He and Chancellor Merkel agreed about the importance of condemning the illegal occupation of government buildings in eastern Ukraine," Cameron's official spokesman told reporters. "They believe the Russian government should be unequivocally condemning that action too."

Cameron is due to speak to French President Francois Hollande about Ukraine later on Monday, said the spokesman. (Reporting by William James; Editing by Andrew Osborn)